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ABSTRACT
This type of turbine evolved from the need to generate power from much lower pressure
heads than are normally employed with the Francis turbine. To satisfy large power demands
very large volume flow rates need to be accommodated in the Propeller turbine, i.e. the
product QH is large. The accurate analysis of performance characteristics of a Propeller
turbine is not possible but it can almost characterized with help of prototype to know most
efficient way to use it. Performance characteristics are the data with the help of which the
exact behaviour and performance of the turbine under different working condition can be
known. These data are plotted in curves from the results of the test performed on the
turbine under different working condition called characteristics curves.
There are six parameters present during working of propeller turbine namely
1. Inlet pressure
2. Head
3. Volume rate flow
4. Turbine speed
5. Shaft power
6. Spear valve position
To achieve the objectives first experiment is performed keeping constant inlet pressure and
under varied load and different position of guide blades and second experiment is
performed keeping fixed guide vane, under varied load and three different inlet pressures
for propeller type Kaplan turbine. Graphs are plotted to analyse the performance
characteristics of Kaplan turbine.
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INTRODUCTION
The Kaplan turbine is a propeller-type water turbine which has adjustable blades. It was
developed in 1913 by the Austrian professor Viktor Kaplan, who combined automatically
adjusted propeller blades with automatically adjusted wicket gates to achieve efficiency
over a wide range of flow and water level. The Kaplan turbine was an evolution of the
Francis turbine. Its invention allowed efficient power production in low-head applications
that was not possible with Francis turbines. The head ranges from 10-70 meters and the
output from 5 to 120 MW. Runner diameters are between 2 and 8 meters. The range of the
turbine is from 79 to 429 rpm. Kaplan turbines are now widely used throughout the world in
high-flow, low-head power production.Kaplan turbines are widely used throughout the
world for electrical power production. They cover the lowest head hydro sites and are
especially suited for high flow conditions. Inexpensive micro turbines on the Kaplan turbine
model are manufactured for individual power production with as little as two feet of head.Large Kaplan turbines are individually designed for each site to operate at the highest
possible efficiency, typically over 90%. They are very expensive to design, manufacture and
install, but operate for decades.
The objectives of this experiment is
To study the performance characteristics of Propeller Turbine at constantinletpressure and under varied load and different position of guide blades.
To study the performance characteristics of Propeller Turbine at fixed guide
vane,under varied load and three different inlet pressures.
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THEORETICAL PRINCIPLES
The reaction turbine operates with its wheel submerged in water. The water before entering
the turbine has pressure as well as kinetic energy. The moment on the wheel is produced by
both kinetic and pressure energies. The water leaving the turbine has still some of the
pressure as well as kinetic energy.
The primary features of the reaction turbine are:
(1) only part of the overall pressure drop has occurred up to turbine entry, the remaining
pressure drop takes place in the turbine itself;
(2) the flow completely fills all of the passages in the runner, unlike the Pelton turbine
where, for each jet, only one or two of the buckets at a time are incontact with the water;
(3) pivotable guide vanes are used to control and direct the flow;
(4) a draft tube is normally added on to the turbine exit; it is considered as anintegral part of
the turbine.
The pressure of the water gradually decreases as it flows through the runner andit is the
reaction from this pressure change which earns this type of turbine its appellation.
This type of turbine evolved from the need to generate power from much lower pressure
heads than are normally employed with the Francis turbine. To satisfylarge power demands
very large volume flow rates need to be accommodated in theKaplan turbine, i.e. the
product QHis large. The overall flow configuration from radial to axial. Figure 9.16 is a part
sectional view of a Kaplan turbine in which theflow enters from a volute into the inlet guide
vanes which impart a degree of swirlto the flow determined by the needs of the runner. The
flow leaving the guide vanesis forced by the shape of the passage into an axial direction and
the swirl becomesessentially a free vortex, i.e
=
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FIG. 9.16. Part section of a Kaplan turbine in situ (courtesy Sulzer Hydro Ltd, Zurich
The vanes of the runner are similar to those of an axial-flow turbine rotor but designed with
a twist suitable for the free-vortex flow at entry and an axial flow at outlet. Because of the
very high torque that must be transmitted and the large length of the blades, strength
considerations impose the need for large blade chords. As a result, pitch/chord ratios of 1.0
to 1.5 are commonly used by manufacturers and, consequently, the number of blades is
small, usually 4, 5 or 6. The Kaplan turbine incorporates one essential feature not found in
other turbine rotors and that is the setting of the stagger angle can be controlled. At part
load operation the setting angle of the runner vanes is adjusted automatically by a servo
mechanism to maintain optimum efficiency conditions. This adjustment requires acomplementary adjustment of the inlet guide vane stagger angle in order to maintain an
absolute axialflow at exit from the runner.
Just upstream of the runner the flow is assumed to be a free-vortex and the velocity
components are accordingly:
c = K/r c = a constant
The relations for the flow angles are
tan = U/c tan = r/c K/(rc )
tan = U/c = r/c .
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Fig. 2 Section of a Kaplan turbine and velocity diagrams at inlet to and exit from the runner.
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EXPERIMENTAL SETUP
Fig. 3 Experimental system in lab Kaplan turbine
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OBSERVATION
1st
CASE
Constant Inlet Pressure(P4)=0.45 bar
Sr.
no.
Turbine
speedp Flow rate
Hydraulic
power
Turbine
powerEfficiency
Area at
inlet
Area at
throat
RPM BAR m3/s W W % m2 m2
1 1420 0.51 0.0030763 138.433 13 9.390817 0.000907 0.000314
2 1120 0.51 0.0030763 138.433 13 9.390817 0.000907 0.000314
3 1015 0.51 0.0030763 138.433 15 10.83556 0.000907 0.000314
4 920 0.5 0.003046 137.069 16 11.67294 0.000907 0.000314
5 815 0.5 0.003046 137.069 17 12.40249 0.000907 0.000314
6 660 0.49 0.0030154 135.692 14 10.31751 0.000907 0.000314
7 500 0.46 0.0029216 131.472 10 7.606173 0.000907 0.000314
8 375 0.46 0.0029216 131.472 9 6.845556 0.000907 0.000314
9 250 0.45 0.0028897 130.035 7 5.383155 0.000907 0.000314
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2nd
CASE
Constant Inlet Pressure (P4)=0.5 bar
Sr.
no.
Turbinespeed
p Flow rate Hydraulicpower
Turbinepower
Efficiency Area atinlet
Area atthroat
RPM BAR m3/s W W % m2 m2
1 1810 0.6 0.0033367 166.835 2 1.198787 0.000907 0.000314
2 1700 0.59 0.0033088 165.439 8 4.835614 0.000907 0.000314
3 1600 0.58 0.0032806 164.031 12 7.315683 0.000907 0.000314
4 1500 0.58 0.0032806 164.031 18 10.97352 0.000907 0.000314
5 1400 0.58 0.0032806 164.031 23 14.02173 0.000907 0.000314
6 1250 0.59 0.0033088 165.439 15 9.066776 0.000907 0.000314
7 1120 0.59 0.0033088 165.439 19 11.48458 0.000907 0.000314
8 1040 0.58 0.0032806 164.031 19 11.58316 0.000907 0.000314
9 900 0.56 0.0032236 161.178 20 12.40862 0.000907 0.000314
10 820 0.56 0.0032236 161.178 20 12.40862 0.000907 0.000314
11 660 0.55 0.0031947 159.733 16 10.01674 0.000907 0.000314
12 530 0.52 0.0031063 155.315 13 8.370074 0.000907 0.000314
13 400 0.52 0.0031063 155.315 11 7.08237 0.000907 0.000314
14 270 0.5 0.003046 152.299 8 5.252821 0.000907 0.000314
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GRAPHS
0
2
4
6
8
10
12
14
16
0 500 1000 1500 2000
Efficiency%
Turbine Speed (RPM)
Efficiency vs Turbine Speed
efficieny for 0.5 bar
efficiency for 0.45 bar
0
5
10
15
20
25
0 500 1000 1500 2000
TurbinePower(w)
Turbine Speed(RPM)
Turbine power vs turbine speed
0.45 BAR
Series2
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DISCUSSIONS
The discussions on the experimental results are :
Nature of graphs
At constant inlet pressure, under varied load, with turbine speed ranging from 1400to 200 r.p.m the turbine shaft power increases initially until the power reaches to a
maximum value and then decreases. This pattern can be observed in the graph
above.
The turbine efficiency measured at constant inlet pressure, under varied load anddifferent spear valve settings ,with turbine speed ranging from 1400 to 200 rpm
increases as the power increases and the curves for efficiency vs speed follows the
same pattern as that of the curves for power vs speed. Hence the graph plotted
follows a near parabolic pattern.
The efficiency is directly proportional to the turbine shaft power, which is provedexperimentally as both parameters when measured against speed behave in same
manner(from graphs).
The power output of turbine shaft is less than theoretical output due to wind age,mechanical friction, and non-uniform flow.
It is seen that the efficiency, generally increases with increase in turbine power. Insome cases, where hydraulic power is increased abnormally, the efficiency
decreases.
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CONCLUSIONS
The following can be concluded from the propeller turbine experiment:
Shaft power
The maximum power output of turbine measured at 0.45 bar pressure, came whenthe valve was fully open and it was 17w at 815 rpm.
The maximum power output of turbine measured at 0.50 bar pressure, came whenthe valve was fully open and it was 23w at 1400 rpm.
Efficiency
The maximum efficiency of the turbine calculated when operated at 0.45 barpressure when the turbine power was maximum and it was 12.40%.
The maximum efficiency of the turbine calculated when operated at 0.50 barpressure when the turbine power was maximum and it was 14.02%.
From the graphs we can conclude that the efficiency is directly proportional to the turbine
shaft power, which is proved experimentally as both parameters when measured against
speed behave in same manner.
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SAMPLE CALCULATION
Turbine speed N = 1810rpm
Inlet pressure = 0.5bar
Now,flow rate
2
2
1A
2A
1
1
2CvAQv
hgm
Cv= 0.97 ; = 1000 kg/m3
A2 = 0.000314 m2
A1 = 0.000907 m2
m= 13600 kg/m3
Putting the values,
So, Q = 0.0033367 m3/s
Water power = Pi Q =0.5105 0.0033367m3/s
=166.835 W
Turbine shaft power =18W
Also, Efficiency =.
100
= 1.198787%
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REFERENCES
1. http://www.me.metu.edu.tr/courses/me402/EXPERIMENT/ME-402EXP2final.pdf
2. en.wikipedia.org/wiki/Kaplan_turbine
3. Fluid Mechanics and Thermodynamics of Turbo Machinery
4.